Primitive people are just as wrong as you

I was reading a fascinating book called Sick Societies, by Robert Edgerton. I came across this thought-provoking tidbit:

Weston LaBarre has provided compelling evidence that the antiquity of a belief is no assurance of its "tested truth," as he put it, nor does its survival demonstrate that it serves any positive purpose. To illustrate these points, LaBarre refers to the ancient and widespread idea that the fundamental source of semen, and thus fertility and life, is the brain. After documenting the importance of this belief from its origin during the Paleolithic to modern times, LaBarre shows that it led countless populations throughout the world to become headhunters in order to eat the brains of others because it was thought that doing so would enhance their own life essence and fertility. The great antiquity and virtual ubiquity of this demonstrably false belief and lethal practice led LaBarre to coin the term "group archosis" to refer to "nonsense and misinformation so ancient and pervasive as to be seemingly inextricable from our thinking.” He concluded, "A frightening proportion of all culture is arguably archosis, more especially sacred culture." French anthropologist Dan Sperber has taken a similar position by asserting that while some mental dispositions have been selected for in the process of biological evolution, others are mere "side effects" that have only marginal adaptive value. Provocatively, Sperber concluded that religion is one of these side effects of evolution.